1. Field of the Invention
The invention relates to a reservoir, particularly for receiving a reducing agent for metering into the exhaust gas tract of an internal combustion engine.
2. Description of the Prior Art
In vehicles with internal combustion engines, the pollutant NOx, among others, has to be reduced because of the increasingly stringent laws on exhaust gases that will come into effect in the next few years. One method that is used is SCR (selective catalytic reduction), in which the pollutant NOx is reduced to N2 and H2O with the aid of liquid reducing agent. The liquid reducing agent is stored in a tank and is pumped by the delivery module from the tank to the metering module via a line. Since the reducing agent freezes below a temperature of −11° C., the tank must be equipped with a heater. This heater is switched on as needed and thaws the frozen reducing agent. The heater and a sensor unit are accommodated in a pot. This pot, which simultaneously acts as a slosh pot, as positioned inside the tank. Since there is always an air cushion above the liquid, the tank on principle begins to freeze from the tank base upward. Because of the ice formation, the slosh pot is initially firmly held to the base of the tank.
Since the reducing agent on freezing expands by approximately 10% of its original volume, the slosh pot must be flexibly fixed to the tank cap. If because of the volumetric expansion the frozen reducing agent presses against the tank cap, the tank cap can yield upward because of the flexible fixation of the slosh pot. Thus damage to the slosh pot from ice pressure is precluded. The provision employed thus far requires that the slosh pot be locked in the lower region of the tank and coupled flexibly to the tank cap in the upper region. The locking in the lower region is very complicated to achieve, especially because the corresponding tanks are made by the blowing method, and thus at least one additional welding operation is also required.
From European Patent Disclosure EP 1 561 016, a method for posttreatment of the exhaust from an internal combustion engine is known in which a liquid reducing agent is used as an aid in treatment. If the temperature of the liquid reducing agent drops below a critical value, a partially chemical conversion of the reducing agent in a substance that lowers the freezing point of the reducing agent is brought about.